soudage plasma par trou de serrure à polarité variable

OBS: Voir la fiche soudage par trou de serrure.

CONT: The conventional method for starting such a weld was to drill a pilot hole to serve as the initial keyhole, carefully align the welding torch over the pilot hole, adjust the standoff distance, and then turn on the torch at full power. ... The new starting technique does not depend on precise manual alignment. The welding torch is positioned with no more than the usual care. As the torch begins to move along the weld, the welding current is gradually increased toward the full operating level, causing the depth of the weld to increase gradually until the keyhole is formed ... . The standoff is controlled by the automatic-voltage-control portion of the welding equipment. At the end of a circumferential weld, the torch can continue a short distance past the starting point to overlap and thereby complete the weld in the starting transition region.